Photocatalysts prepared from layered clays and titanium hydrate for degradation of organic pollutants in water

Abstract

Reaction between titanium hydrate sol of strong acidity and four smectite clays were utilized to create composite nanostructures of titanium dioxide (TiO2) and silicate nanoparticles. The acidic sol solution reacts with the clay platelets and leaches out part of the magnesium or aluminum in the clay, while the sol particles hydrolyze further, yielding larger precursors of TiO2 nanoparticles and condense on the fragmentised pieces of the leached silicate. Moreover, introducing PEO surfactants into the synthesis can significantly increase the porosity and surface area of the composite solids. The TiO2 in the product are crystal grains of several nanometres in size. They disperse on silicate plates or are separated by silicate fragments and voids such that they are accessible to organic molecules. The mechanism of the synthesis reaction is distinguishingly different from conventional pillaring process. The composite solids provide highly effective photocatalysts for the degradation of phenol and synthetic dyes in aqueous solution. © 2004 Elsevier B.V. All rights reserved.